French voters began voting on Sunday in the second round of general elections expected to hand president Francois Hollande's Socialist party a clear parliamentary majority.

Polling stations opened at 8:00 am (4:00pm AEST) and are to close 12 hours later in the main cities across France.

Voters are to choose 541 deputies, with 36 already having been elected in the first round vote on June 10.

Opinion polls released before the end of campaigning at midnight on Friday showed Mr Hollande's Socialists and their parliamentary allies on track to take control of France's lower house National Assembly.

Mr Hollande, who defeated right winger Nicolas Sarkozy in May's presidential election, has urged voters to give him a majority as he seeks to steer France through Europe's debt crisis, rising unemployment and a faltering economy.